What is the ruling on a woman whose husband has died putting scented oil on her hair, knowing that the scent disappears as soon as the hair is washed?

A woman observing her 'iddah (waiting period) after her husband's death is forbidden from using any kind of perfume. She is allowed to wash and comb her hair, but she must not use anything considered a fragrance. Therefore, she is not permitted to use the aforementioned oil if it has a pleasant scent.